V22.0436 - Prof. Grishman

Lecture 19: Trends in High-Performance Computer Architecture

Taking advantage of technology improvements

How has the steady progress in integrated circuit technology been
translated
into improvements in processor performance?

The technology improvements lead to faster transistors and smaller
transistors.
Faster transistors mean faster clock times. Smaller transistors mean
that
we can put more transistors on a chip (a Core 2 Duo has about 300M
transistors). (Moore's Law -- transistor counts double about every two
years.) What can we do with the increasing number of transistors
to improve performance?

increase the width of the data we process. The first
microprocessor
(Intel
4004) had 4-bit data paths; later processors had wider paths. However,
it doesn't help much to increase processing beyond 32 or 64-bit units.

power also a concern in large data centers and for small portable
computers (netbooks, app-phones)

Together these factors limit overall CPU performance

Next step is multiple cores (several processors on a chip)

natural path to making use of addl transistors to increase
throughput without increasing clock freq

introduced for x86 architecture on AMD Opteron in 2005, then by
Intel (Core 2 Duo and Quad)

while superscalar was limited by the degree of microparallelism
of sequential programs, but did not require any reprogramming or
redesign, using multiple cores or processors requires some program
redesign to take advantage of high-level
parallelism (multiple processes), but can achieve large gains for some
tasks